In silico validation revealed the role of SCN5A mutations and their genotype-phenotype correlations in Brugada syndrome

BACKGROUND

Brugada syndrome (BrS) is a rare genetic disease that causes sudden cardiac death (SCD) and arrhythmia. SCN5A pathogenic variants (about 30% of diagnosed patients) are responsible for BrS.

AIMS

Lack of knowledge regarding molecular characteristics and the correlation between genotype and phenotype interfere with the risk stratification and finding the optimal treatment in Vietnam. Therefore, we identified SCN5A variants and evaluated the genotype-phenotype correlation of BrS on 117 Vietnamese probands.

MATERIALS AND METHODS

The clinical characteristics and blood samples of BrS patients were collected. To determine SCN5A variants, Sanger sequencing was conducted, and subsequently, these variants were analyzed by bioinformatic tools.

RESULTS

In this cohort, the overall rate of detected variants in SCN5A was 25.6%, which could include both pathogenic and benign variants. In genetic testing, 21 SCN5A variants were identified, including eight novels and 15 published variants. Multiple bioinformatic tools were used to predict variant effect with c.551A>G, c.1890+14G>A, c.3338C>T, c.3578G>A, and c.5484C>T as benign, while other variants were predicted as disease-causing. The family history of SCD (risk ratio [RR] = 4.324, 95% CI: 2.290-8.269, p < 0.001), syncope (RR = 3.147, 95% CI: 1.668-5.982, p = 0.0004), and ventricular tachycardia/ventricular fibrillation (RR = 3.406, 95% CI: 1.722-5.400, p = 0.0035) presented a significantly higher risk in the SCN5A (+) group, consisting of individuals carrying any variant in the SCN5A gene, compared to SCN5A (-) individuals.

CONCLUSION

The results contribute to clarifying the impact of SCN5A variants on these phenotypes. Further follow-up studies need to be carried out to understand the functional effects of these SCN5A variants on the severity of BrS.

Mutation spectrum of retinoblastoma patients in Vietnam

BACKGROUND

Retinoblastoma (RB), an intraocular malignancy commonly diagnosed in children, is mostly caused by inactivating mutations of both alleles of the RB1 gene. Early genetic screening for RB1 gene mutations would greatly improve treatment outcomes and patient management.

METHODS

In this study, both somatic and germline mutations were detected in blood and tumour samples of 42 RB patients using direct sequencing and multiplex ligation-dependent probe amplification.

RESULTS

In total, 34 different mutations were found in 36 patients, including 1 SNP, 4 large deletions, 5 splicing sites, 1 missense, 7 frameshifts and 17 nonsense mutations. There were five novel mutations and one unreported which have not been found in large databases such as Leiden Open Variation Database (LOVD) and ClinVar.

CONCLUSION

A higher rate of RB patients carrying heterozygous germline mutation and highly prevalent with pathogenic truncated mutation, hence, early detection of RB is essential for vision salvation and genetic counselling.

Targeted next‐generation sequencing determined a novel SGCG variant that is associated with limb‐girdle muscular dystrophy type 2C: A case report

Limb‐girdle muscular dystrophy‐type 2C (LGMD2C) is caused by mutations in the SGCG gene. Here, we report a case of a 26‐year‐old male who had inactive walking due to proximal muscle weakness. Targeted next‐generation sequencing found a novel variant c.412C > T (Q138*) in the SGCG gene.

Bone infection: a clinical priority for clinicians, scientists and educators

Bone infection has received increasing attention in recent years as one of the main outstanding clinical problems in orthopaedic-trauma surgery that has not been successfully addressed. In fact, infection may develop across a spectrum of patient types regardless of the level of perioperative management, including antibiotic prophylaxis. Some of the main unknown factors that may be involved, and the main targets for future intervention, include more accurate and less invasive diagnostic options, more thorough and accurate debridement protocols, and more potent and targeted antimicrobials. The underlying biology dominates the clinical management of bone infections, with features such as biofilm formation, osteolysis and vascularisation being particularly influential. Based on the persistence of this problem, an improved understanding of the basic biology is deemed necessary to enable innovation in the field. Furthermore, from the clinical side, better evidence, documentation and outreach will be required to translate these innovations to the patient. This review presents the findings and progress of the AO Trauma Clinical Priority Program on the topic of bone infection.

Abstract P5-04-03: Palbociclib synergizes with autophagy inhibitors to induce senescence in breast cancer

This abstract was withdrawn by the authors.

Progression of spinal deformity in wheelchair-dependent patients with Duchenne muscular dystrophy who are not treated with steroids

We determined the frequency, rate and extent of development of scoliosis (coronal plane deformity) in wheelchair-dependent patients with Duchenne muscular dystrophy (DMD) who were not receiving steroid treatment. We also assessed kyphosis and lordosis (sagittal plane deformity). The extent of scoliosis was assessed on sitting anteroposterior (AP) spinal radiographs in 88 consecutive non-ambulatory patients with DMD. Radiographs were studied from the time the patients became wheelchair-dependent until the time of spinal fusion, or the latest assessment if surgery was not undertaken. Progression was estimated using a longitudinal mixed-model regression analysis to handle repeated measurements.

Scoliosis ≥ 10° occurred in 85 of 88 patients (97%), ≥ 20° in 78 of 88 (89%) and ≥ 30° in 66 of 88 patients (75%). The fitted longitudinal model revealed that time in a wheelchair was a highly significant predictor of the magnitude of the curve, independent of the age of the patient (p <  0.001). Scoliosis developed in virtually all DMD patients not receiving steroids once they became wheelchair-dependent, and the degree of deformity deteriorated over time.

In general, scoliosis increased at a constant rate, beginning at the time of wheelchair-dependency (p < 0.001). In some there was no scoliosis for as long as three years after dependency, but scoliosis then developed and increased at a constant rate. Some patients showed a rapid increase in the rate of progression of the curve after a few years – the clinical phenomenon of a rapidly collapsing curve over a few months.

A sagittal plane kyphotic deformity was seen in 37 of 60 patients (62%) with appropriate radiographs, with 23 (38%) showing lumbar lordosis (16 (27%) abnormal and seven (11%) normal).

This study provides a baseline to assess the effects of steroids and other forms of treatment on the natural history of scoliosis in patients with DMD, and an approach to assessing spinal deformity in the coronal and sagittal planes in wheelchair-dependent patients with other neuromuscular disorders.

Cite this article: Bone Joint J 2014;96-B:100–5.

[Gestational diabetes insipidus during a twin pregnancy]

Gestational diabetes insipidus is an uncommon clinical disease whose prevalence is approximately two to three pregnancies per 100,000. It may be isolated or associated with preeclampsia. We report a case of gestational diabetes insipidus in a twin pregnancy, originally isolated during two months, and secondarily complicated by HELLP-syndrome. We recall the specific pathophysiology of polyuric-polydipsic syndrome during pregnancy and summarize its various causes. Finally, we discuss the indications, in case of isolated gestational diabetes insipidus, of treatment by dDAVP.

[Vitamin D and pregnancy]

Vitamin D plays a key role in calcium-phosphorus homeostasis and bone metabolism, but it is also involved in numerous others tissues. Vitamin D deficiency among pregnant women is frequent in many populations over the world. It is associated with an increased risk of preeclampsia, gestational diabetes mellitus, and caesarean section. Consequences in newborns are low birth weight, neonatal rickets, a risk of neonatal hypocalcemia, asthma and/or type 1 diabetes. Therefore, prevention of vitamin D deficiency among pregnant women is essential. The currently recommended supplementation amount of vitamin D is not sufficient to maintain a value of 25 hydroxy vitamin D above 30 ng/ml, during pregnancy. Randomized controlled trials during pregnancy are necessary to evaluate the amount of vitamin D sufficient to avoid the consequences of vitamin D deficiency.

Circulating melanoma cells and survival in metastatic melanoma

A validated assay for the enumeration of circulating melanoma cells (CMCs) may facilitate the development of more effective therapies for metastatic melanoma patients. In this study CD146+ cells were immunomagnetically enriched from 7.5 ml of blood. Isolated cells were fluorescently stained with DAPI, anti-molecular weight melanoma-associated antigen (HMW-MAA), anti-CD45 and CD34 and Ki67. CMCs were identified as CD146+, HMW-MAA+, CD45-, CD34-, Ki67-/+ cells. Eighty-eight percent of spiked SK-MEL28 cells in 7.5 ml blood were recovered. In all 55 healthy donors ≤1 CMCs were detected in 7.5 ml of blood. A retrospective analysis was conducted comparing CMC counts and overall survival in 79 blood samples from 44 melanoma patients. CMCs ranged from 0 to 8,042 per 7.5 ml. Two or more CMCs were detected in 18 (23%) of the patients and 30-100% (mean 84%) of the CMCs expressed the proliferation marker Ki67. Patients with ≥2 CMCs per 7.5 ml of whole blood, as compared with the group with <2 CMCs, had a shorter overall survival (2.0 months vs. 12.1 months, P=0.001).

Survey of Vietnamese peanuts, corn and soil for the presence of Aspergillus flavus and Aspergillus parasiticus

Aspergillus flavus and Aspergillus parasiticus cause perennial infection of agriculturally important crops in tropical and subtropical areas. Invasion of crops by these fungi may result in contamination of food and feed by potent carcinogenic aflatoxins. Consumption of aflatoxin contaminated foods is a recognised risk factor for human hepatocellular carcinoma (HCC) and may contribute to the high incidence of HCC in Southeast Asia. This study conducted a survey of Vietnamese crops (peanuts and corn) and soil for the presence of aflatoxigenic fungi and used microsatellite markers to investigate the genetic diversity of Vietnamese Aspergillus strains. From a total of 85 samples comprising peanut (25), corn (45) and soil (15), 106 strains were isolated. Identification of strains by colony morphology and aflatoxin production found all Vietnamese strains to be A. flavus with no A. parasiticus isolated. A. flavus was present in 36.0% of peanut samples, 31.1% of corn samples, 27.3% of farmed soil samples and was not found in virgin soil samples. Twenty-five per cent of the strains produced aflatoxins. Microsatellite analysis revealed a high level of genetic diversity in the Vietnamese A. flavus population. Clustering, based on microsatellite genotype, was unrelated to aflatoxin production, geographic origin or substrate origin.

Functional diversity of motoneuron dendrites: by accident or design?

The distribution and geometry of the dendritic trees of spinal motoneurons obey several well-established rules. Some of these rules are based on systematic relationships between quantitative geometrical features (e.g. total dendritic length) and the three-dimensional trajectory followed by dendrites from their origin to their termination. Since dendritic geometry partially determines the transmission of current and voltage signals generated by synapses on the dendritic tree, our goal was to compare the efficacy of signal transmission by dendritic trajectories that followed different directions. To achieve this goal, we constructed detailed compartmental models of the dendritic trees of intracellularly stained neck motoneurons and calculated the electrotonic properties of each soma-to-terminal trajectory. These properties displayed a high degree of variability. To determine if this variability was due, in part, to the orientation (e.g. rostral, rostral-dorsal-lateral) of the trajectory, each trajectory was classified according to its orientation. The attenuation of current and voltage signals en route to the soma were strongly related to trajectory orientation. Trajectories with similar attenuation factors formed functional subunits that were arranged in distinct domains within the ventral horn. The difference in the efficacy of signal transmission between subunits was increased by activation of neighbouring synapses due to trajectory-related differences in non-linear summation. These results indicate that the input-output properties of motoneurons depend on the direction of the path taken by dendrites from their origin at the cell body to their terminals.

Survey of Vietnamese coffee beans for the presence of ochratoxigenic Aspergilli

Vietnamese coffee beans were investigated for the presence of ochratoxigenic Aspergilli. Ninety-three percent of the coffee samples studied were positive for A. niger. No other ochratoxigenic species were present. HPLC analysis determined that 8.7% of the A. niger strains were positive for ochratoxin A (OA) production. There was no significant difference in the level of contamination or incidence of toxigenic strains in samples that had been rejected by manual sorting and those that were destined for human consumption. No OA-producing fungi were uncovered in a fresh coffee bean sample analysed, suggesting that the OA problem most likely occurs post-harvest.

Effect of nonlinear summation of synaptic currents on the input-output properties of spinal motoneurons

A single spinal motoneuron receives tens of thousands of synapses. The neurotransmitters released by many of these synapses act on iontotropic receptors and alter the driving potential of neighboring synapses. This interaction introduces an intrinsic nonlinearity in motoneuron input-output properties where the response to two simultaneous inputs is less than the linear sum of the responses to each input alone. Our goal was to determine the impact of this nonlinearity on the current delivered to the soma during activation of predetermined numbers and distributions of excitatory and inhibitory synapses. To accomplish this goal we constructed compartmental models constrained by detailed measurements of the geometry of the dendritic trees of three feline motoneurons. The current "lost" as a result of local changes in driving potential was substantial and resulted in a highly nonlinear relationship between the number of active synapses and the current reaching the soma. Background synaptic activity consisting of a balanced activation of excitatory and inhibitory synapses further decreased the current delivered to the soma, but reduced the nonlinearity with respect to the total number of active excitatory synapses. Unexpectedly, simulations that mimicked experimental measures of nonlinear summation, activation of two sets of excitatory synapses, resulted in nearly linear summation. This result suggests that nonlinear summation can be difficult to detect, despite the substantial "loss" of current arising from nonlinear summation. The magnitude of this "loss" appears to limit motoneuron activity, based solely on activation of iontotropic receptors, to levels that are inadequate to generate functionally meaningful muscle forces.

Semi-quantitative RT-PCR method to estimate full-length mRNA levels of the multidrug resistance gene

Expression levels of P-glycoprotein (P-gp), the transporter encoded by the human multidrug resistance gene (MDR1), may play an important role in drug disposition. The ability to quantitate full-length MDR1 mRNA levels may be predictive of P-gp expression and function. Therefore, a semi-quantitative RT-PCR assay was developed to assess full-length MDR1 mRNA levels. Levels offull-length 3.8-kb MDR1 mRNA were estimated by comparing PCR amplification of the RNA extract with that of an internal standard, deltaMDR1. The 2.9-kb deltaMDR1 competitor RNA standard was constructed by deleting 965 bpfrom the interior of MDR1 mRNA. The full-length MDR1 and deltaMDR1 share identical 5' and 3'primer binding sequences, allowing for their simultaneous amplification in the same RT-PCR. With this approach, MDR1 mRNA levels can be sensitively and reliably estimated with a detection limit of 2000 copies. Full-length MDR1 mRNA levels in various human cell lines and lymphocytes from leukemia patients varied over 100-fold, ranging from 0.3 to 36.5 x 10(5) copies/microg total RNA. The semi-quantitative full-length RT-PCR assay may be useful in estimating MDR1 mRNA levels to assess P-gp expression, which may be important in studying the role of P-gp in drug disposition and cancer chemotherapy efficacy.

Undermethylated DNA as a source of microsatellites from a conifer genome

Developing microsatellites from the large, highly duplicated conifer genome requires special tools. To improve the efficiency of developing Pinus taeda L. microsatellites, undermethylated (UM) DNA fragments were used to construct a microsatellite-enriched copy library. A methylation-sensitive restriction enzyme, McrBC, was used to enrich for UM DNA before library construction. Digested DNA fragments larger than 9 kb were then excised and digested with RsaI and used to construct nine dinucleotide and trinucleotide libraries. A total of 1016 microsatellite-positive clones were detected among 11 904 clones and 620 of these were unique. Of 245 primer sets that produced a PCR product, 113 could be developed as UM microsatellite markers and 70 were polymorphic. Inheritance and marker informativeness were tested for a random sample of 36 polymorphic markers using a three-generation outbred pedigree. Thirty-one microsatellites (86%) had single-locus inheritance despite the highly duplicated nature of the P. taeda genome. Nineteen UM microsatellites had highly informative intercross mating type configurations. Allele number and frequency were estimated for eleven UM microsatellites using a population survey. Allele numbers for these UM microsatellites ranged from 3 to 12 with an average of 5.7 alleles/locus. Frequencies for the 63 alleles were mostly in the low-common range; only 14 of the 63 were in the rare allele (q < 0.05) class. Enriching for UM DNA was an efficient method for developing polymorphic microsatellites from a large plant genome.

Dendritic cells from nonobese diabetic mice exhibit a defect in NF-kappa B regulation due to a hyperactive I kappa B kinase

Insulin-dependent diabetes mellitus (IDDM) is characterized by the T cell-mediated destruction of insulin-producing beta cells. Accordingly, APCs, such as macrophage, have also been shown to be important in the disease process. However, the role(s) of dendritic cells (DCs) that exhibit potent APC function remains undefined in IDDM. Here we demonstrate that DCs derived from nonobese diabetic (NOD) mice, a model for IDDM, are more sensitive to various forms of stimulation compared with those from C57BL/6 and BALB/c mice, resulting in increased IL-12 secretion. This property is a consequence of hyperactivation of NF-kappaB, a transcription factor known to regulate IL-12 gene expression. Specifically, NOD DCs exhibit persistent hyperactivation of both IkappaB kinase and NF-kappaB in response to stimuli, in addition to selective degradation of IkappaBepsilon. Transfection of NOD DCs with a modified form of IkappaBalpha significantly reduced IL-12 secretion, suggesting that hyperactivation of NF-kappaB was in part responsible for increased IL-12 production. An enhanced capacity of NOD DCs to secrete IL-12 would be expected to contribute to the development of pathogenic Th1 (Tc1) cells during the diabetogenic response.

Molecular typing of pathogenic fungi

In this Round Table, the application of several methods of molecular typing were discussed in reference to four important pathogenic fungi: Coccidioides immitis, Histoplasma capsulatum, Candida albicans and Paracoccidioides brasiliensis. Among the different methods the following were discussed: restriction fragment length polymorphisms (RFLP), single nucleotide polymorphisms, random amplified polymorphic DNA (RAPD), polymerase chain reaction (PCR)-RFLP and microsatellites. By means of these methods, several important biological questions related to speciation, mode of reproduction and population genetics could be approached. The basic information obtained from this approach has implications in the understanding of these pathogenic fungi in relation to their behavior and the development of pathogenic features, such as resistance to antimicrobials and virulence factors used for colonization of mammalian hosts. The knowledge obtained from these studies could also be used for the development of innovative diagnostic methods, as well as for novel therapeutic approaches and production of vaccines.